Issue link: https://iconnect007.uberflip.com/i/1531384
40 DESIGN007 MAGAZINE I JANUARY 2025 The Pulse Feature Column by Martyn Gaudion, POLAR INSTRUMENTS As we enter the second quarter of the 21st century, there appears to be a new chapter in PCB technology. Ultra high density intercon- nect (UHDI) has become a buzzword, but it's actually not that new; many of the processes were already established in the high-volume production of Asian cellphones and tablets. What is new and challenging, however, is migrating the line widths and stackups—once the domain of handheld consumer products— into the lower volume specialized environment of the commercial world. In the high-volume world, the quantities mean that prototyping and fine-tuning are more economical, given that unit produc- tion volumes will be in the hundreds of thou- sands or millions. Low- and medium-volume manufacture is more complex as the econom- ics mean that prototyping can be expensive. Trace widths have languished between 50–75 microns for several years, but the drip of prog- ress is pushing into the 10–40-micron arena. New Chemistries, New Processes Modified semi-additive process (mSAP) and semi-additive process (SAP) are emerging with some leading-edge PCB fabricators. Once reserved for organic substrate interposers (as a lower-cost alternative to silicon interposers), these processes are now seen on specialist PCBs. Traces are vertical, and the copper foils are thin to match the shrink-down in trace widths. Ultra Upgrade Unknowns: What's Coming for UHDI?